(a) Field of the Invention
This invention relates to a process and a composition for controlling undesirable vegetation. More particularly, the present invention is directed to a process for controlling the growth of velvetleaf by applying Colletotrichum spores thereto.
This invention also relates to the growing of a fungus, Colletotrichum coccodes (Wallr.) Hughes, collecting spores, concentrating the spores and formulating the spores for application over geographic areas to control undesirable vegetation, namely velvetleaf (Abutilon theophrasti Medic.). According to the invention, after application the spores germinate, infect the velvetleaf and result in a pathogenic disease which terminates or reduces the growth of the undesirable plant.
(b) Description of Prior Art
Velvetleaf, often called button-weed or elephant-ear, is an erect annual broadleaf plant species from 0.3 to 3 m in height, but generally grows to just above the crop in which it is growing. It is a prolific seed producer with 17,000 seeds per plant being produced on average. The seeds can persist in the soil for up to 50 years and are unaffected by passage through animals or by ensilement.
Velvetleaf is widely distributed throughout most of the United States and much of southeastern Canada. It is considered as one of the most common and costly weeds in the North Central region of the United States. This weed species occurs in waste places, vacant lots, gardens and cultivated fields. Velvetleaf is a serious weed problem in corn, soybeans, cotton, wheat, oats, barley, sugarbeets, sunflower, tomato and other cultivated crops. Infestations of this weed presently cause significant yield reductions in these crops and the problem is increasing due to the prolific seed production of velvetleaf and the difficulty in the control thereof.
In most cropping systems, chemical herbicides have been developed to provide acceptable to excellent control of many grass and broadleaf weeds. However, widespread and continuous use of certain herbicides has favored the establishment of problem, difficult to control weeds such as velvetleaf. A combination of chemical herbicides and cultivation are presently used to control velvetleaf populations in various crops, but these methods are inadequate for the control of velvetleaf as infestations of this weed are continuing to increase in size and in number. Problems with cultivation for the control of velvetleaf include:
1. appropriate timing to avoid injury to the crop plants is difficult; PA0 2. lack of control of late germinating plants; PA0 3. it cannot be used in new cropping systems such as solid seeded soybeans (SSS). PA0 1. lack of soil persistence resulting in no control of late germinating velvetleaf; PA0 2. most chemical herbicides cause some detrimental effects to the growth of the crop; PA0 3. chemical herbicides may adversely affect non-target organisms; PA0 4. toxic residues of chemical herbicides may persist in the environment or contaminate our food.
The problems associated with the present chemical herbicides for velvetleaf control include:
Dingley, J. M. and Gilmour, J. W., New Zeal. J. For. Sci. 2(2): 192 (1972) discloses the C. coccodes (Wallr.) Hughes fungus in order to distinguish it from the C. acutatum, to which the studies refer. Stevenson, W. R., Evans, G. E., and Barksdale, T. H., P1. Dis. Rept. 62(11): 937 (1978) discloses the losses in fresh market tomato crops produced by anthracnose disease caused by C. coccodes (Wallr.) Hughes among others, and the development of tomato cultivars with genetic resistance to the disease.
Although many patents deal with the fungal control of vegetation, none of them disclose the use of Colletotrichum coccodes (Wallr.) Hughes for this treatment. Such patents include the following:
______________________________________ U.S. Pat. Nos.: ______________________________________ 3,087,865 Drake et al 3,300,390 Tiner et al 3,308,038 Rhodes et al 3,150,062 Greenberg et al 3,357,895 Cherry 3,361,555 Herschler 3,999,973 Templeton 4,061,488 Mann 4,162,912 Charudattan 4,390,360 Walker ______________________________________